
class MixinA:
    def __getattr__(self, item):
       # Process item and return value if known
       if item == 'a':
           return 'MixinA'

       # If it is unknown, pass it along to give
       # a chance to another class to handle it
       return super().__getattr__(item)

class MixinB:
    def __getattr__(self, item):
       # Process item and return value if known
       if item == 'b':
           return 'MixinB'

       # If it is unknown, pass it along to give
       # a chance to another class to handle it
       return super().__getattr__(item)

class Example(MixinA, MixinB):
    # main class
    pass

e  = Example()
print(e.c)